Causation is the relationship that exists between cause and effect.
In Logic we distinguish between two different forms of causation:
As an example of necessary causation, consider catching influenza: in order to come down with the flu, you must first be exposed to the flu virus. Thus, the necessary cause of getting the flu is being exposed to the virus. But notice that just because you are exposed to the virus does not mean you will get the flu (your immune system might be strong enough to fight it off). So, being exposed to the flu is a necessary condition (you cannot get the flu without it), but it is not a sufficient condition (just because your exposed does not mean you will get sick).
Sufficient causation is stronger than necessary causation in that if a sufficient cause exists, the connected consequence must follow. However, a sufficient cause is not exclusive of other possible causes of the same event. For example, the chemical reaction fire can be cause by striking a match, flicking a lighter, or focusing a beam of sunlight through a magnifying glass. Each one is sufficient to bring about the effect.
The relationship between sufficient and necessary causation can be expressed logically in an hypothetical (or conditional) proposition (i.e., an “if/then” statement). The element of the proposition following the word ‘if’ is called the antecedent and the element following the word ‘then’ is called the consequent: “If X then Y.” The antecedent always represents a sufficient condition for the consequent, while the consequent represents a necessary condition for the antecedent.
In Metaphysics causation is the rational explanation of an event: event X explains why event Y happened.
If an event is limited in time (i.e., it has a beginning and an end) it is said to be a contingent event. As such, there is, even if it is unknown to us, an explanation of the event, there is a reason why it happened, there is a cause preceding its occurrence. Or, more simply put, every contingent event is, in principle, explainable.
In pre-philosophical culture causation was usually associated with gods, ancestors, spirits, or some other ontologically distinct “other”. The beginning of the Western Philosophical tradition (known as Natural Philosophy, or Presocratic Philosophy) began as an attempt to replace the mythological account (muthos) of causation with rational (logos) one. The belief that there is a knowable set of causes in the world is distinctly rooted in the Greek rejection of the mythological world view.
The Natural Philosophers offered various theories of causation, but the 4th Century BCE Aristotle synthesized them into a four-fold account of causation:
According to Aristotle, to have knowledge of some event, to know a thing, is to fully grasp all four causes of the event/thing.